Over the past 15 years, numerous studies have established the use of 199,201Tl in the field of nuclear medicine. 201Tl is used for myocardial perfusion imaging and evaluation of coronary artery disease, while occasionally 199Tl is also useful in nuclear medicine. Various methods have been proposed for production of 201Tl/199Tl [1-3]. All of these methods are based on proton/alpha irradiation on lead/thallium target.
Qaim et al. (S. M. Qaim, R. Weinreich, H. Ollig, Int. J. Appl. Radiat. Isot. 30 (1979) 85) separated 201Tl and 203Pb by anion exchanger Dowex 1. Walt et al. (T. N. van der Walt and C. Naidoo, Radiochem. Acta, 88 (2000) 185) teaches a method based on ion exchange chromatography for recovery of 201Tl and its precursor 201Pb from proton bombarded natural thallium cyclotron targets using Bio-Rex 70 cation exchanger. Nayak et al. (Dalia Nayak et. al, Appl. Radiat. Isot., 57 (2002) 483) teaches separation of no-carrier-added thallium radionuclide from the bulk target matrix gold by liquid-liquid extraction using trioctylamine as a liquid anion exchanger. In the method of Jammaz et al. (I. L. Jammaz, J. K. Amartey, A. F. Namor, M. M. Vora and R. M. Lambrecht, Radiochem. Acta, 88 (2000) 179) thallium radionuclides are separated by liquid-liquid extraction using p-tert-butylcalix-4-arene derivative. In all of these processes large numbers of organic compounds and organic solvents are involved. It is always better to avoid organic solvents as most of them are toxic and carcinogenic to human health.
Nayak et al. (Dalia Nayak et. al, Green Chemistry, 4 (2002) 581) separated no-carrier-added thallium radionuclide from the bulk target matrix gold by two algal genera, Lyngbya major and Rhizoclonium hicroglyphicum. Though in this process less chemicals were used, but collection and culture of the algae throughout the year is a difficult task.
In all the methods discussed above large numbers of chemicals are involved in the process of separation of thallium radionuclides from its precursor lead and mercury radionuclides. As thallium radionuclides are often used in vivo, contamination from other chemicals in patient's body is highly undesired.
Since 199Tl as well as 201Tl are highly useful radionuclides in the field of nuclear medicine, and lead and/or mercury radionuclides, in no-carrier-added form are associated with all the production methods of 199Tl/201Tl radionuclides. Thus 199Tl/201Tl needs to be separated from lead or/and mercury in an easy and cost effective manner without the use of hazardous chemicals.
The present inventors have now found that separation of thallium radionuclides is achieved by using ultra pure water (Milli Q) water in conjunction with dialysis sac without use of organic solvents/hazardous chemicals and thus avoiding the drawbacks of other prior art methods.